"Soft" tissue patterning: muscles and tendons of the limb take their form.

The musculoskeletal system grants our bodies a vast range of movements. Because it is mainly composed of easily identifiable components, it serves as an ideal model to study patterning of the specific tissues that make up the organ. Surprisingly, although critical for the function of the musculoskeletal system, understanding of the embryonic processes that regulate muscle and tendon patterning is very limited. The recent identification of specific markers and the reagents stemming from them has revealed some of the molecular events regulating patterning of these soft tissues. This review will focus on some of the current work, with an emphasis on the roles of the muscle connective tissue, and discuss several key points that addressing them will advance our understanding of these patterning events.